CN-122026046-A - Ultra-wideband 3dB quadrature hybrid coupler based on lumped elements

CN122026046ACN 122026046 ACN122026046 ACN 122026046ACN-122026046-A

Abstract

The invention discloses an ultra-wideband 3-dB quadrature hybrid coupler based on lumped elements, and belongs to the technical field of microwave integrated circuits. The coupler comprises an input port P1, two output ports P2 and P3, an isolation port P4, four basic coupler units LC balun and an LC four-port coupling network. By combining the unbalanced-balanced LC balun structure with the LC four-port coupling network, the quadrature hybrid coupling function with 3-dB power distribution and 90-degree phase difference is realized in the ultra-wideband frequency range. Compared with the traditional quadrature coupling structure, the invention has the advantages of few design parameters, compact structure, excellent amplitude balance, port isolation and phase consistency in a broadband, and is suitable for a broadband radio frequency front-end system with high performance and high integration level.

Inventors

LI JIANHUA
YAO XUEDONG
ZHANG YAFANG
WANG JIAFENG

Assignees

阜阳师范大学

Dates

Publication Date: 20260512
Application Date: 20260202

Claims (6)

1. The ultra-wideband 3dB quadrature hybrid coupler based on the lumped elements comprises a first input port P1, a second two output ports P2, a third output port P3, a fourth isolation port P4, a first LC balun, a second LC balun, a third LC balun, a fourth LC balun and a LC four-port coupling network, and is characterized in that the core structure of the four-port network is a symmetrical lumped element lattice network, a parallel LC resonance circuit is connected between central nodes of the lattice network, the parallel LC resonance circuit is formed by connecting an inductor L1/alpha and a capacitor alpha C1 in parallel, and the resonance frequency of the parallel LC resonance circuit is configured to be equal to the design central frequency f c of the coupler.
2. The wideband 3-dB quadrature hybrid coupler of claim 1, wherein the base coupling element LC balun structure is comprised of two inductive elements and two capacitive elements, wherein a first inductive element first end is electrically connected to the input port IN, a first inductive element second end is electrically connected to the first capacitive element first end, the first capacitive element second end is grounded, a second inductive element first end is grounded, a second end is electrically connected to the second capacitive first end, and a second capacitive element second end is electrically connected to the first inductive element first end.
3. The broadband 3-dB quadrature hybrid coupler of claim 1, wherein the LC four-port coupling network structure is composed of two inductive elements L1/2, two capacitive elements 2C1 and a parallel LC resonant circuit, wherein the LC four-port coupling network structure has a first inductive element and a second inductive element electrically connected in series, the first capacitive element and the second capacitive element are electrically connected in series, and the parallel LC resonant circuit is electrically connected between the first inductive element and the second inductive element and a junction point where the first capacitive element and the second capacitive element are electrically connected in series.
4. A wideband 3-dB quadrature hybrid coupler as claimed in claim 3, wherein the inductance and capacitance element values in the parallel LC tank circuit are set to L1/α and αc1, respectively, where α is an adjustable parameter for adjusting the resonant frequency and network response characteristics. By adjusting the design parameter α, a collaborative optimization can be made between the operating bandwidth, passband magnitude ripple, and the degree of balance between the output ports P2 and P3. The value range of the optimization coefficient alpha is more than or equal to 0.5 and less than or equal to 1.5.
5. The wideband 3-dB quadrature hybrid coupler of claim 4, wherein the optimization factor α has a value of 1.137, such that the coupler achieves good performance with an amplitude imbalance of less than 0.58 dB and a phase imbalance of less than 0.2 ° in the band range of 21 GHz to 39 GHz, while both the input return loss S11 and the inter-port isolation S41 are better than 30 dB.
6. Lumped element wideband 3-dB quadrature hybrid coupler as claimed in any of claims 1 to 5, characterized in that it is suitable for use in mixer, balanced amplifier and phase shifter networks in microwave systems, providing wideband operation and miniaturization advantages.

Description

Ultra-wideband 3dB quadrature hybrid coupler based on lumped elements Technical Field The invention relates to the technical field of microwave and radio frequency integrated circuits, in particular to a broadband and miniaturized 3-dB quadrature (90 DEG) hybrid coupler for microwave and millimeter wave bands, which is particularly suitable for Ka-band Monolithic Microwave Integrated Circuit (MMIC) design. Background The quadrature hybrid coupler is used as a basic microwave element and widely applied to a balance amplifier, an image rejection mixer, a phase shifter, a beam forming network and other radio frequency systems so as to realize equal power distribution and accurate 90-degree phase difference of signals. The performance, particularly the operating bandwidth, port isolation, amplitude/phase balance, and physical size, directly determines the overall performance of the associated system. Conventional quadrature hybrid couplers are often implemented using distributed transmission line structures, such as branch line couplers or ring couplers. Such a structure is based on a quarter-wavelength transmission line, and the physical length of the lambda/4 transmission line is inversely proportional to the operating frequency, and particularly, the lambda/4 transmission line occupies a larger circuit area in a lower frequency band, so that the urgent requirements of a modern communication system on high integration and miniaturization are difficult to meet. Furthermore, the inherent characteristics of classical distributed architecture limit its operating bandwidth, and generally achieve good performance over only a relatively narrow frequency range, making it difficult to cover ultra-wideband or multi-band application scenarios. The lumped element structure breaks through the limitation of the physical length of the transmission line, and can theoretically realize the circuit function in a size far smaller than the wavelength. However, how to stably achieve excellent amplitude balance, high isolation and accurate 90 ° phase difference in the ultra-wideband range using lumped elements remains a technical challenge. Existing designs based on lumped elements often face problems of limited bandwidth, significant performance degradation due to high frequency parasitics, complex design process, sensitivity to component value tolerances, and the like. Aiming at the problems, the invention designs an ultra-wideband 3-dB quadrature hybrid coupler based on lumped elements, which comprises an input port P1, two output ports P2 and P3, an isolation port P4, four basic coupler units LC balun and an LC four-port coupling network. By combining the unbalanced-balanced LC balun structure with the LC four-port coupling network, the quadrature hybrid coupling function with 3-dB power distribution and 90-degree phase difference is realized in the ultra-wideband frequency range. Compared with the traditional quadrature coupling structure, the invention has the advantages of few design parameters, compact structure, and excellent amplitude balance, port isolation and phase consistency in a wide frequency band. Disclosure of Invention Aiming at the defects of the prior art, the invention provides the lumped element 3-dB quadrature hybrid coupler which has novel structure, simple design, excellent broadband performance and easy monolithic integration. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: A broadband 3-dB quadrature hybrid coupler based on lumped elements comprises an input port P1, two output ports P2 and P3, an isolation port P4, four basic coupler units LC balun and an LC four-port coupling network. The four LC balun and one LC four-port coupling network form a symmetrical 'lattice' -shaped structure, and the four-port coupling network is characterized in that a resonant LC circuit is connected in parallel between central nodes of the symmetrical structure; Further, the basic coupler LC balun is formed by two pairs of lumped elements L1 and C1, forming an all-pass network that satisfies the relation l1/c1=r2, where R is the port characteristic impedance. The inductance and capacitance values of the parallel resonant circuit are respectively set to be L1/alpha and alpha C1, parameter association is carried out on the parallel resonant circuit and the basic coupler unit through an optimization coefficient alpha, and the bandwidth, the amplitude ripple in the passband and the balance degree between the two output ports P2 and P3 can be optimized through adjusting the value of alpha. Preferably, the value range of α is set to 0.5 to 1.5. More preferably, when the coupling quadrature hybrid coupler is applied to the Ka-band MMIC implementation, the α value is 1.137, and at this time, good performance of having an amplitude imbalance of less than 0.58 dB and a phase imbalance of less than 0.2 ° can be achieved in the frequency band range of 21 GHz to 39 GHz, and both the